Time

The real-world time, date and moon phase affect gameplay. All are determined by your system clock. Technically it is possible to change the clock to get a desired moon phase or time, but this is considered cheating.

Contents

Moon phase and date

Just as in real life, the NetHack world goes through several phases of the moon.[1] Probably unlike real life, these phases have a real effect on gameplay.

The date is only checked when the game is started or restored; if you keep playing without saving, you'll continue to see the effects even after the relevant period has passed (or not see the effects even though it has been reached). NetHack divides the month into eight phases of three or four days each; thus the full and new moon will be reported for a rather longer time than your calendar might depict.

During a full moon:

Your base Luck is increased by one.[2] ("You are lucky! Full moon tonight.")

If a cockatrice uses its hissing attack and you have no lizardcorpse, you will always start turning into stone, rather than having a 1-in-10 chance.[7]

NetHack knows when it is Friday the 13th, and decreases your base Luck by one accordingly.[8] The game gives a warning message: "Watch out! Bad things can happen on Friday the 13th."

If Friday the 13th happens to be a full moon, the modifiers to base Luck will cancel each other out. Between 1995 and 2025, Friday the 13th has occurred or will occur during (NetHack's definition of) a new or full moon on the following days: